Display devices have traditionally used cathode-ray tubes (CRT). Presently, much effort has been made to study and develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDP), field emission displays, and electro-luminescence displays (ELD), as a substitute for CRT displays. LCD devices have certain advantages over the other displays, such as high resolution, light weight, thin profile, compact size, and low power supply requirements.
Generally, an LCD device includes two substrates that are spaced apart and face one another with a liquid crystal material disposed between the two substrates. The two substrates include electrodes that face each other. A voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
Because the LCD device is a non-emissive type display device, a backlight is needed to supply the non-emissive type display device with light. A CCFL (cold cathode fluorescent lamp) or an EEFL (external electrode fluorescent lamp) may be used. Recently, a LED (light emitting diode) has been used because of it's small size, low power consumption and high reliability.
FIG. 1 is an exploded perspective view illustrating an LCD device using an LED according to the related art. In the related art LCD module as shown in FIG. 1, a backlight assembly 20 and a liquid crystal panel 10 are sequentially disposed over a bottom case 50. A main supporter 40 has a rectangular frame shape and supports the backlight assembly 20 and the liquid crystal panel 10. The main supporter 40 may be combined with the bottom case 50.
Gate and source printed circuit board (PCB) 18 and 16 are connected to the liquid crystal panel 10 through a flexible printed circuit (FPC) film. A top cover 60 is disposed on the top of the liquid crystal panel 10. As shown, the top cover 60 has a rectangular frame shape. The top cover 60 presses and fixes a peripheral portion of the liquid crystal panel 10 and is combined with the main supporter 40 and the bottom case 50.
The backlight assembly 20 includes a plurality of LEDs 24, a reflecting sheet 26, a light guide plate 30, and optical sheets 32 such as a prism sheet and/or a diffusion sheet. The LEDs 24 are arranged on a plurality of a base PCBs (metal core printed circuit boards) 22. The base PCBs 22 are arranged in parallel on the bottom case 50. The reflecting sheet 26 has a plurality of through holes 28. The through holes 28 correspond to the LEDs 24. The light guide plate 30 has a plurality of reflecting dots 31. The reflecting dots 31 also correspond to the LEDs 24 or the through holes 28. The optical sheets 32 are spaced apart from the light guide plate 30. The optical sheets 32 condense and diffuse light passing through the light guide plate 30.
A viewer generally watches the LCD device in a standing state, as illustrated in FIG. 2. FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1. The LCD device of FIG. 2 is shown standing vertically to a ground for viewer's convenience. With respect to the standing LCD device, the gate PCB (18 of FIG. 1) is disposed at a side portion of the LCD device, and a source PCB 16 is disposed at a top portion of the LCD device as shown in FIG. 2. A control PCB 70 having a timing controller is connected to the source PCB 16. The control PCB 70 generates control signals for the gate PCB and the source PCB 16 and supplies data signals to the source PCB 16. The control PCB 70 is disposed at an upper portion of the standing LCD device.
The LEDs 24 consume power to generate light, and thus much heat is produced at the LEDs 24. The LEDs 24 may require a substantial amount of power to generate enough light. The heat is accumulated at the upper portion of the standing LCD device by a thermal convention. Accordingly, liquid crystal molecules at the upper portion of the standing LCD device may become deteriorated and/or abnormally arranged. Further, driving circuits, such as the source PCB 16 and the control PCB 70, at the upper portion of the standing LCD device may be abnormally operated based on the effects from the heat.
To resolve these problems, a heat sink 62 may be attached on a rear surface of the bottom case 50. However, because the heat sink 62 is attached on the rear surface of the bottom, it may be difficult to radiate the heat that is accumulated at the upper portion. Further, because the heat sink 62 has a basic body and a plurality of pins that protrude from the basic body, the LCD device may have an increased thickness due to the presence of the heat sink 62.